Method of forming transparent layers for a solar cell

Abstract

Disclosed herein are devices, systems, and methods for processing a solar cell precursor. The processing may include forming a transparent, electrically conductive first layer over the solar cell precursor. The processing may also include forming a transparent, electrically conductive second layer over the solar cell precursor, preferably in physical contact with the first layer. The first layer may comprise at least indium, zinc, and oxygen and the second layer may comprise oxygen and a greater proportion of indium than the first layer.

The invention claimed is: 
     
       1. A method of processing a solar cell precursor, the method comprising:
 forming a first layer of a stack of at least two solid phase layers over the solar cell precursor, wherein the first layer is transparent and electrically conductive and comprises at least indium, zinc, and oxygen; and 
 forming a second layer of the stack over the solar cell precursor wherein the second layer is transparent and electrically conductive and comprises oxygen and a proportion of indium that is greater than that of the first layer, wherein the second layer is arranged on the solar cell precursor and arranged in the stack between the solar cell precursor and the first layer. 
 
     
     
       2. The method according to  claim 1 , the method further comprising transporting the solar cell precursor while forming the first layer and while forming the second layer. 
     
     
       3. The method according to  claim 1 , wherein the second layer is in physical contact with the first layer. 
     
     
       4. The method according to  claim 1 , wherein a first material flow for forming the first layer and a second material flow for forming the second layer interpenetrate or are exposed to the same process gas. 
     
     
       5. The method according to  claim 1 , wherein the second layer is in physical contact with a semiconductor of the solar cell precursor or an oxide of the semiconductor. 
     
     
       6. The method according to  claim 1 , wherein a stack comprising the first layer and the second layer has a reflection coefficient of less than 10%. 
     
     
       7. The method according to  claim 6 , wherein the reflection coefficient is at a wavelength of 600 nm. 
     
     
       8. The method according to  claim 1 , wherein the first layer comprises a layer thickness that is greater than that of the second layer. 
     
     
       9. The method according to  claim 1 , wherein the second layer comprises a dopant of a chemical compound of indium with oxygen. 
     
     
       10. The method according to  claim 9 , wherein the dopant comprises at least one of tin, zirconium, titanium, cerium, and tungsten. 
     
     
       11. The method according to  claim 1 , wherein the second layer comprises more indium than zinc. 
     
     
       12. The method according to  claim 1 , wherein the forming of the first layer is performed by sputtering a first sputtering target, and wherein the forming of the second layer is performed by sputtering a second sputtering target. 
     
     
       13. The method according to  claim 12 , wherein the first sputtering target or the second sputtering target comprise ceramic. 
     
     
       14. The method according to  claim 1 , the method further comprising covering the solar cell precursor with an additional second layer between the first layer and the second layer, wherein the additional second layer is transparent and electrically conductive, wherein the first layer comprises a layer thickness that is greater than that of the additional second layer. 
     
     
       15. A method of processing a solar cell precursor, the method comprising:
 emitting a first material flow comprising zinc and oxygen toward the solar cell precursor; and 
 emitting a second material flow comprising indium and oxygen toward the solar cell precursor, 
 wherein the emitting of the first material flow and the emitting of the second material flow comprise forming a mixture of materials that coats the solar cell precursor with a layer of the mixture of materials, wherein the mixture of materials is transparent, electrically conductive, and comprises a proportion of indium that decreases through the layer along a direction away from the solar cell precursor. 
 
     
     
       16. The method of  claim 15 , wherein the mixture of materials comprises more indium than zinc. 
     
     
       17. The method of  claim 15 , wherein the proportion of indium decreases continuously through the layer along the direction away from the solar cell precursor.